Forget the 5:2 diet and the Paleo diet, there's a new trend sweeping social media.

Known as the Cinderella diet, it encourages women to drop weight to look like the famous Disney cartoon character.

The Cinderella diet aims for a body mass index of 18, which is classified as medically underweight on the BMI scale - a number which compares your weight to your height, and is calculated by dividing your weight (in kilograms) by your height (in metres squared).

The unhealthy fad, which originated in Japan, is now gaining traction in other countries and is trending on Twitter.

The Cinderella diet aims for a body mass index of 18, which is classified as medically underweight on the BMI scale (pictured Lily James as Cinderella)

Ms Cohen said there were a number of serious health effects which could result from people attempting to reach their 'Cinderella' goal weight

''There is very real chance that people can die from trying to achieve the Cinderella ideal,' she explained.

'Restricting your diet to achieve this low weight is dangerous and you may feel lethargic, experience extreme mood swings, grow unwanted body hair, find it hard to socialise, be at risk of fainting and lose your period,' she added.

She said women who were adopting this ridiculous challenge should seek help from a medical professional.

'When your BMI drops to 18, you're at a seriously high risk of losing healthy function of your body,' said Ms Cohen

'This cinderella diet is a form of eating disorder and needs to be treated as quickly as possible,' said Ms Cohen.

'A BMI under 18.5 places you in the underweight category.

'Eating disorders have the highest death rate of any mental illness, including depression.'

Dietitian Susie Burrell said it was without a doubt one of the most dangerous diets she had heard of.